Commonly-owned, U.S. patent application Ser. No. 08/452,255 filed 26 May 95 by Eldridge, Grube, Khandros and Mathieu (status: now U.S. Pat. No. 6,336,269) and its counterpart PCT patent application number PCT/US95/14909 filed 13 NOV 1995 (status: published as WO95/14909, 06 Jun. 96) disclose methods for making resilient interconnection elements for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire “stem” or “skeleton”) to a terminal on an electronic component, coating the flexible core element and adjacent surface of the terminal with a “shell” of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element may be used to effect pressure, or demountable, connections between two or more electronic components, particularly microelectronic components, including semiconductor devices.
The aforementioned PARENT CASE discloses fabricating spring contact elements by depositing at least one layer of metallic material into openings defined in multiple masking layers deposited on a surface of a substrate which may be an electronic component such as an active semiconductor device. Each spring contact element has a base end, a contact end, and a central body portion. In an embodiment disclosed therein, the contact end may be offset in the z-axis (at a different height) and in at least one of the x and y directions from the base end. In this manner, a plurality of spring contact elements are fabricated in a prescribed spatial relationship with one another on the substrate. The spring contact elements make temporary (i.e., pressure) or permanent (e.g., joined by soldering or brazing or with a conductive adhesive) connections with terminals of another electronic component to effect electrical connections therebetween. In an exemplary application, the spring contact elements are disposed on a semiconductor devices resident on a semiconductor wafer so that temporary connections can be made with the semiconductor devices to burn-in and/or test the semiconductor devices prior to their being singulated from the semiconductor wafer.
As in the PARENT CASE, the present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. As used herein, the term “fine-pitch” refers to microelectronic devices that have their terminals disposed at a spacing of less than 5 mils, such as 2.5 mils or 65 μm. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.
Commonly-owned, U.S. patent application Ser. No. 08/955,001 filed 20 Oct. 97 by Eldridge, et al. (status: now U.S. Pat. No. 6,043,563), incorporated by reference herein, also addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. As described therein, spring contact elements may be fabricated at areas on an electronic component which are remote from terminals to which they are electrically connected, and electrically connected to the terminals via conductive lines which extend from terminals of an electronic component to positions which are remote from the terminals. In this manner, a plurality of substantially identical spring contact elements can be mounted to the electronic component so that their free ends are disposed in a pattern and at positions which are spatially-translated from the pattern of the terminals on the component. The spring contact elements include, but are not limited to, composite interconnection elements and plated-up structures. The electronic component includes, but is not limited to, a semiconductor device, a memory chip, a portion of a semiconductor wafer, a space transformer, a probe card, a chip carrier, and a socket.